Islamabad (AP) - Defying a warning from Washington, Pakistan's prime minister promised to go ahead with a plan to import natural gas from Iran, even if the U.S. levies additional sanctions against the Mideast country.

Prime Minister Yousuf Raza Gilani's comments Tuesday came two days after the U.S. special envoy to Pakistan, Richard Holbrooke, cautioned Pakistan not to "overcommit" itself to the deal because it could run afoul of new sanctions against Iran being finalized by Congress.

The deal has been a constant source of tension between the two countries, with Pakistan arguing it is vital to its ability to cope with an energy crisis, and the U.S. stressing it would undercut international pressure on Iran over its nuclear program.

Gilani said Pakistan would reconsider the deal if it violated U.N. sanctions, but the country was "not bound to follow" unilateral U.S. measures. He said media reports that quoted him as saying Pakistan would heed Holbrooke's warning were incorrect.

The U.N. has levied four sets of sanctions against Iran for failing to suspend uranium enrichment, a process that can produce fuel for a nuclear weapon. The latest set of U.N. sanctions was approved earlier this month.

The U.S. has also applied a number of unilateral sanctions against Iran, and Congress is finalizing a new set largely aimed at the country's petroleum industry. Both houses have passed versions of the sanctions and are working to reconcile their differences.

Pakistan and Iran finalized the gas deal earlier this month. Under the contract, Iran will export 760 million cubic feet (21.5 million cubic meters) of gas per day to Pakistan through a new pipeline beginning in 2014. The construction of the pipeline is estimated to cost some $7 billion.

While U.S. officials have expressed opposition to the deal, Washington acknowledges that Pakistan faces a severe energy crisis and has made aid to the energy sector one if its top development priorities. Electricity shortages in Pakistan cause rolling blackouts that affect businesses and intensify suffering during the hot summer months.

U.S. opposition to the gas deal has also been tempered by Washington's reliance on Pakistani cooperation to fight al-Qaida and Taliban militants staging attacks against NATO troops in Afghanistan.

The Pakistani military is also engaged in fierce battles with Taliban fighters along the Afghan border who have declared war against the state.

Pakistani troops backed by fighter jets killed 43 militants and wounded two dozen others in the Orakzai tribal region Tuesday, said Jahanzeb Khan, the deputy political administrator in the area.

Four soldiers were killed in the fighting and 18 others were wounded, said Khan.

The military declared victory against the Taliban in Orakzai at the beginning of June, but regular clashes with the militants have continued.

Meanwhile, a purported Pakistani Taliban spokesman warned the group would kill 35 Pakistani soldiers unless the government agreed to a demand to release captured militants.

"We have 35 Frontier Corps men in our custody and we will start killing them if our arrested fellows are not released soon," Ikramullah Mohmand told The Associated Press over the phone from undisclosed location.

Mohmand did not mention how many militants the group wanted freed and refused to give a deadline, but said "we will not wait for long."

He confirmed the paramilitary soldiers were the same ones who went missing after a militant attack on a border checkpoint in Mohmand tribal region more then a week ago. Six Frontier Corps soldiers were killed in the attack.

Attempts to reach a spokesman for the military were not immediately successful.

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Associated Press writers Munir Ahmed in Islamabad and Hussain Afzal in Parachinar and Anwarullah Khan in Peshawar contributed to this report.

Defying a warning from Washington, Pakistan's prime minister promised to go ahead with a plan to import natural gas from Iran, even if the U.S. levies additional sanctions against the Mideast country.